Whereas the Earth is the home of a variety of organic-based lifeforms, the planet of Cybertron is the homeworld of a race of robots which have the ability to transform into other mechanisms, with each Transformer having its own unique disguise. The Transformers are divided into two separate camps: the good and just Autobots, who are led by Optimus Prime (whose disguise is a red 18-wheel semi truck); and the evil Decepticons, who are led by Megatron (who transforms into a gun; there's a good deal of size-shifting involved with Megatron as well). With fuel supplies (called Energon Cubes) on Cybertron running low, both forces travel through space looking for a new source, which leads them to Earth, which from their perspective is rich in the minerals and chemicals they need. Disguising themselves as cars, airplanes, boats, etc. easily recognizable to humans, the Transformers engage in a secret war for control of Earth's bountiful natural resources...
This secret war explodes into action when Spike Witwicky, the descendant of a 19th century sailor, buys a yellow sports car which turns out to be an Autobot named Bumblebee. What Spike doesn't know is that the eyeglasses he inherited have a secret map burned into the lens by the evil Decepticon leader, Megatron. This map details the location of a mysterious power source which could turn the course of the war between the two factions of Transformers. Meanwhile, the war begins with an attack by Scorponok, a giant scorpion-like Decepticon, on a military base in the Middle East, as the various Transformers on both sides awake to wage war on Earth.